C. T. Jackson on Emery in Chester, Mass. 89 
the investing coat being from half an inch to two inches in 
thickness. Tt is found extremely difficult to break up these 
very slow and laborious, ast no grip can be had on their rounde 
su 
sit of which the e great emery bed also cuts. On this hill ie 
emery is more largely Siesta and less mixed with magnetic 
iron ore. It is e like corundum, but still contains the com- 
bined protoxyd “of | iron, charsnariatia of true emery. Its spe- 
cific gravity is from - 75 to 8°80, while that from the South 
oaniain is from 402 to 4:37; Naxos amend Sina: from 3°71 to 
wai analysis of bd coarsely pretine emery of the 
N orth Mountain, Chester. Sp. er. Bes 
i: - +) 46°50 
Protoxyd firm, <= 32 oe eee 
ieee 60 ee eee 5-00 
Silica & loss, - - - - . . My 4°50 
Emery of the South hill.’ Sp. es 402. H. ap! 
Alum - 45°50 
Pen of iron, a ee eee ee 
ca & titanic acid, ese ed, & cil! eee ee 
100-00 
Beziing the oxyd of iron which can be er io out — 
y acids as accidental, and that which cann SO 
as an essential constituent, we shall have a the oma 
: “© The highest specific gravity of any sample from the South mountain was #3144. 
_ Ast. Jour. Sor.—Szcoxp Sznres, Vor. XXXIX, No. 115.—Jan., 1868. 
; 12 
